Newsletter - 2015 bois-marie INSTITUT DES HAUTES ÉTUDES SCIENTIFIQUES

editorial What is the point of basic China is also emerging as a leader in R&D funding ($600bn research? This question is by 2020), with very significant support for basic research. This often asked of those who have a curiosity-driven rather than a is a key political issue. utilitarian approach to their work. As well as its decisive role in most technological innovations One way to answer this is to show the continuum that exists and its impact on economic players, basic research contributes from basic to applied research. As we celebrate this November to deep thinking. Whether solving the mysteries of black holes the centenary of Einstein describing General Relativity, we or of morphogenesis, theoretical sciences are some of the most recall that without this breakthrough, our GPS systems would powerful tools to understand the world better. The scientific operate with the required degree of precision for about two method is driven by a desire to push the boundaries of knowledge, minutes only, once activated. Many technological innovations in which is also a desire for independence and freedom - two of the aerospace industry, telecommunications or medical research IHÉS’ core values. involve extremely complex theoretical models. Basic research is The Institute is a place of knowledge and sharing, led by its more than ever a strategic issue for companies. faculty and visiting professors. IHÉS is more than ever determined The socio-economic impact of a reputedly abstract discipline such to fully play its part within the scientific ecosystem, by offering as mathematics has recently been measured in France: the study exceptional scientists a place where their research can flourish. (published in May 2015) gives proof positive that mathematics This Bois-Marie will give you an idea of their intellectual contributes to the creation of added value up to 15% of GDP. curiosity and of the thriving scientific activity at the Institute. A similar result was found in studies in the UK in 2012 and in Supporting the IHÉS model for the benefit of the entire scientific the Netherlands in 2013 (16% and 13% respectively). A report community is essential. published by the American Academy of Arts and Sciences in the United States in 2014 has no hesitation in stating that the Marwan Lahoud country’s entire economy has greatly benefited from massive Chairman of the IHÉS Board of Directors investment in science and engineering in the 20th century.

contents

events ...... 2 - 5 cours de l’IHÉS ...... 6 testimony ...... 7 “séminaire de géométrie algébrique” ...... 8 - 10 Oppenheimer and IHÉS ...... 11 - 13 international campaign ...... 14 - 15 point of view of ... / agenda ...... 16

Institut des Hautes Études Scientifiques | Le Bois-Marie, 35 route de Chartres, F-91440 Bures-sur-Yvette, France Telephone: +33 1 60 92 66 00 | Email: [email protected] | Website: www.ihes.fr events quantum mechanics trimester

For the first time at IHÉS, Thibault Damour, There were 37 speakers during this trimester, Jürg Fröhlich and David Ruelle organised a including Alain Connes, Alain Aspect, Serge trimester on Quantum Mechanics. Haroche, Claude Cohen-Tannoudji, Jean Dalibard. Many of the most important experiments that test fundamental predictions or puzzling aspects of Quantum Mechanics have been carried out by research groups in France, in particular ones working in the Paris area. Furthermore, theoretical work on the foundations of Quantum Mechanics has a Pierre Cartier, Thibault Damour, long-standing tradition in France, which Claude Cohen-Tannoudji has continued to this day. Finally, problems concerning the unification of quantum theory quantum sciences. It was held over 11 weeks with a theory of gravitation are actively with an opening colloquium on 29 January, then pursued by people in the Paris area and, in a weekly seminar from 4 February to 1 April particular, at IHÉS. with talks and discussions around a specific The program brought together experimental topic. It ended with a closing colloquium and theoretical physicists with an expertise in on 9 April. Serge Haroche

Join our 2000+ subscribers to view most of the scientific events on the IHÉS YouTube channel. summer school

The summer school was organised by Joanna an overview of recent developments in the Nelson, Daniel Cristofaro-Gardiner and Joël theory of moduli spaces of pseudoholomorphic Fish and was held from 6 to 17 July. curves in symplectic and contact geometry. This year, 7 mini lectures with moderated This Summer School, on Moduli Problems discussions and related talks by a senior researcher in Symplectic Geometry, aims to provide PhD on current and future directions in the field students, post-docs, and young researchers with were added to the programme.

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Dusa McDuff with Summer School participants

2 Huawei conference quantum gravity in Paris The Quantum Gravity in Paris workshop meets once a year for four days, including a special day at IHÉS. Over the years, the workshop has led to new collaborations between researchers and strengthened ties among the research institu- tions involved in its organisation. 2015 freshers’ welcome for FMJH Masters’ students Located since 1962 in the Chevreuse valley at Stéphane Mallat Cédric Villani the heart of the world’s largest pool of mathe- maticians, the Institute has always maintained As part of the partnership with Huawei, IHÉS Francis Bach, Cédric Villani, Mérouane Debbah close relations with the French mathematical and Huawei Technologies France’s Mathematical and Stéphane Mallat were invited to speak community and is delighted to be organising and Algorithmic Sciences Lab organised their during this day of meetings and exchanges collaborative events such as welcoming Masters’ first joint conference on 15 May, in the Marilyn among researchers from both institutions. students. On 2,3 and 4 September 2015, IHÉS and James Simons Conference Centre. welcomed nearly 90 students for a joint start to the academic year, organised by the Jacques Hadamard Mathematics Foundation, for Univer- sité Paris-Sud, Université Versailles St Quentin, ENS Cachan, ENSTA and École Centrale Paris. a day to explore Alexander Grothendieck Maxim Kontsevich’s contributions Alexander Grothendieck, who passed away on Ahmed Abbes and Emmanuel Ullmo organised 13 November 2014 in Ariège (South-West of an inaugural conference day, broadcasted Friends of IHES took advantage of Maxim France), left a profound mark on the history of simultaneously at the Morningside Center of ­Kontsevich’s visit to the United States to receive mathematics. Hailed as one of the most influential Mathematics, the Chinese Academy of Sciences his Breakthrough Prize in Mathematics to mathematicians of the 20th century, his ambitious and the Department of Mathematical Sciences, ­organise a conference on his work. This event programme of bringing together arithmetic, Tokyo University. took place at the Simons Foundation on algebraic geometry and topology continues to 18 November. structure contemporary mathematics. Two of Maxim’s close colleagues, Tony Pantev and Anton Kapustin, explored some of his Alexander Grothendieck was one of the first contributions to mathematics and their permanent professors at IHÉS at its creation in ­interactions with physics. 1958 and remained there for 11 years. He set up the extraordinary “Séminaire de Géométrie random maps day Algébrique”. Grothendieck was demanding, original and Since the early 2000’s, there has been generous and those qualities shaped the spirit increased interest in the study of random of the Institute.The name of the Institut des maps in ­theoretical physics, combinatorics Hautes Études Scientifiques is inextricably and ­probabilities. In order to bring together linked to Grothendieck’s. scientists working in this field and to facilitate IHÉS wanted to pay tribute to him and interactions between maths and physics, special ­inaugurated on 21 January, in partnership with “random maps days” have been held on a CNRS, the “Laboratoire Alexander Grothendieck” regular basis since 2006 and almost bi-monthly where all mathematical and theoretical physics since 2012. fields will be covered. The two last days were held at IHÉS. The laboratory was established as a Certified Research Team (ERL) and enables the fruitful Emmanuel Ullmo historical relations between IHÉS and CNRS to perpetuate.

3 events the new Université Paris-Saclay

Université Paris-Saclay was officially created scientific potential that is recognised in France on 29 December 2014 and brings together 19 and internationally as being first rate. The Institutions of higher education and research, ambition of this project is to create a major among which IHÉS. research university based on the development of a continuum from basic to applied sciences using As a world famous centre of scientific research the skills, diversity and wealth of experience of and a driving force for innovation and ­economic the various players. Emmanuel Ullmo, development, Université Paris-Saclay is a major IHÉS has naturally chosen to be one of its scientific, economic and territorial project for founding members and is proud to have taken elected Member of France and Europe. Since 2008, 19 research part in this project from its creation. Academia­ Europaea organisations (two universities, École Normale Supérieure, six research institutes and 10 In July 2014, Emmanuel Ullmo was invited to engineering and business grandes écoles) have become one of the 278 new members of the decided to join forces within the Paris-Saclay Academia Europaea, including 13 in the mathe- Campus Foundation to create the Université matics section. The mathematicians Paris-Saclay. Jean Bourgain, Jean-Pierre Bourguignon, These 19 founding institutions are of a diverse Mikhail Gromov, Maxim Kontsevich and Cédric nature yet complementary. Together, they offer Villani, all connected with IHÉS, are among the a very high standard of training and, through existing members of the Academia Europaea’s interdisciplinary activities, they combine a mathematics section.

Maxim Kontsevich Professor Maxim Kontsevich was elected as foreign associate of the National Academy of Sciences in April in recognition of his contributions to fundamental research. He also received an Honorary Doctorate from the University of Vienna on 11 June, with 5 other laureates.

high school students visit IHÉS

Regional educational mathematics inspectors the history of gravitation conception, from from the Versailles Academy organised a Aristotle to string theory. Pierre Pansu, morning session at the Institute on 11 April mathematician and professor at Université for high school students, so that they could Paris-Sud showed several “Histoires courtes” Celebration in the Great Hall of the University of Vienna learn more about research in mathematics in which researchers explain their activities, and theoretical physics. and then commented these on the basis of his 100 students from 33 high schools from the own experience. The many questions asked by entire Academy visited the IHÉS’ facilities. the students were a mark of their interest in They then attended two conferences. Pierre these topics and IHÉS is delighted to provide Vanhove, physicist and CEA senior researcher this type of interaction between researchers at IHÉS, presented a conference on Gravitation and the general public. Attractiveness during which he explained

4 arrival of Francis Bach

University of California Berkeley (where he was awarded the Eli Jury Award for the best thesis in signal processing) under the supervision of The sources of inspiration for theoretical Professor Michael Jordan. In 2007, he spent two sciences are many: from questions lying at the years in the Mathematical Morphology group very foundation of sciences to issues arising at École des Mines de Paris, and then joined from developments in industry. the WILLOW project-team at INRIA/École It is on this particular point that Schlumberger, Normale Supérieure until 2010. a long-time partner with whom a relationship His area of research is statistical machine learning, of trust and mutual respect has been built especially in graphical models, artificial vision, since 1994, wished to support IHÉS. The largest Francis Bach image and signal processing, bioinformatics and French donor of the Fiftieth Anniversary brain. He develops tools for processing massive ­Campaign therefore created the Schlumberger Francis Bach is currently a researcher at INRIA and complex data sets. Chair for mathematical sciences at IHÉS in 2006. and has been leading since 2011 the SIERRA Among many other prizes and scientific awards, Chair holders are invited to the Institute for project team, which is part of the IT Department he received the Microsoft Research Fellowship research visits, in order to undertake research at École Normale Supérieure. in 2002 (awarded to 12 students in the US relating to topics at the interface with high After studying at École Polytechnique, he joined each year) and the INRIA Prize for young technology. the Corps National des Mines (Paris). He then researchers in 2012. Francis Bach is the holder of the Schlumberger obtained an MSc in Applied Mathematics at Chair for mathematical sciences at IHÉS, starting École Normale Supérieure (Cachan). In 2005, from 1 September for a period of 6 months. he completed his PhD in Computer Science at other IHÉS Chair holders Schlumberger Chair for mathematical sciences at IHÉS Felix Otto, mathematician, Max-Planck- Institut in den Naturwissenschaften, Leipzig (Deutschland). Les Amis de l’IHÉS Israel Gelfand Chair Spencer Bloch, mathematician, University Les Amis de l’IHÉS, an association aiming to a lecture: “Living theories, theories of the living”, of Chicago (USA). raise awareness of IHÉS within a wider audience, followed by a musical interlude by pianist Francis Brown, mathematician, All Souls once again held two public conferences this year. Paloma Kouider. He addressed the questions College, Oxford University (UK). emerging from the huge progress made in Samson Shatashvili, physicist, Hamilton IHÉS welcomed for the first time on Thursday 6 genome sequencing and functional analysis over Mathematical Institut, Trinity, Dublin November Jean-Louis Etienne, a one-of-a-kind the years. He also mentioned the ubiquity of (Ireland). scientist who shared his experience as passionate cognitive systems in the living world and their Louis Michel Chair polar explorer with the public. His talk, “The possible links with as yet poorly understood Ali H. Chamseddine, physicist, American antarctic circumpolar current, a major factor in the phenomena such as aging. About 60 people University of Beirut (Lebanon). climate?” was illustrated by a slideshow of pictures attended this fascinating lecture. Eliezer Rabinovici, physicist, Hebrew taken during his expedition. The conference University of Jerusalem (Israel). was followed by a debate with a large audience. On 25 June, Yves Barral from ETH Zurich gave René Thom Chair Robert C. Penner, mathematician, California Institute of Technology (USA), Aarhus University (Denmark), University of Tokyo (Japan) and MPIM, Bonn (Deutschland).

Yves Barral

Jean-Louis Étienne

5 cours de l’IHÉS testimony

The Cours de l’IHÉS, a scientific activity initiated in 2013 by the new director, were created with the aim of teaching current research in total freedom to anyone interested, and helping with the dissemination of scientific knowledge.

The Cours de l’IHÉS are given by permanent professors, senior researchers holding positions at IHÉS, chair holders, or invited professors from other institutions. They generally focus on speakers’ recent work but are also the opportunity to present the latest developments in a major research topic. Lectures are free of charge and open to everyone, within space constraints. Videos of the lectures are all available online on the Institute’s YouTube channel.

The 2014-2015 programme offered many lectures straddling both mathematics and theo- retical physics, in the tradition of this specific feature at IHÉS, which gives rise to fruitful exchanges between mathematicians and theoretical physicists.

Vasily Pestun (permanent professor, IHÉS): Masaki Kashiwara (RIMS, Kyoto) - Pierre Quantum Gauge Theories and Integrable Systems Schapira (Université Paris 6): Indsheaves, Temperate Holomorphic Functions and Irregular Mikhail Gromov (permanent professor, Riemann-Hilbert Correspondence IHÉS): Probability, Symmetry, Linearity Dennis Gaitsgory Dennis Gaitsgory (Harvard Univ.): Singular Maxim Kontsevitch (permanent professor, Support of Coherent Sheaves IHÉS): Exponential Integral Mathieu Lewin (Université Paris-Dauphine): Samson Shatashvili (Trinity College Dublin Mesures de Gibbs non linéaires et leur dérivation & IHÉS): Supersymmetric Vacua and Integrability à partir de la mécanique quantique

Francis Brown (CNRS-IHÉS): Périodes motiviques et groupe de Galois cosmique

Mathieu Lewin

Ofer Gabber, Vasily Pestun Masaki Kashiwara Samson Shatashvili

6 testimony

Francis Brown studied at the University of Manin conjecture on moduli spaces of curves, Cambridge, then at ENS in Paris. After his Hoffman’s conjecture on multizeta functions doctorate, he went on short visits to the Max- and the Deligne-Ihara conjecture on mixed Planck Institute for Mathematics in Bonn and Tate motives over Z. to the Mittag-Leffler Institute in Stockholm, as Part of Francis Brown’s research revolves part of the Post-Doctoral European Institute around questions arising from quantum field programme. He joined the CNRS in 2007 and theory, especially the “cosmic Galois group” obtained the CNRS bronze medal in 2012. He programme, which was started by many also received in the same year the Élie Cartan people connected with IHÉS, in particular Prize from the Académie des Sciences de Paris Pierre Cartier, Alain Connes, Maxim Kontsevich Christophe Soulé, Francis Brown, Don Zagier for his “proof of two conjectures relating to and Dirk Kreimer. multiple zeta values”. This is a programme that seeks to reinterpret Having been a visiting professor, conference Francis Brown’s work lies at the intersection the theory of renormalisation in physics speaker, CNRS senior researcher at IHÉS, of algebraic geometry and arithmetic. He with Grothendieck’s motivic Galois theory. It and Chair holder, Francis Brown talks of his has worked in particular on motivic periods, enables perturbative quantum field theory to ­experience as a researcher at IHÉS. especially multizeta functions. His contribu- be studied from an algebraic geometry point tions include: the resolution of the Goncharov- of view.

time for me: I had just finished my thesis, so I same time, as well as people from outside – who joined the bandwagon. It’s exhilarating to be can change as the sessions progress, since the riding the crest of the wave rather than to be videos are now freely accessible. The lectures swimming against the tide. have a very special atmosphere: participants ask The idea to linking Grothendieck’s motives many very precise questions. You can sense their with Feynman’s theory is an idea that was born interest in the subject. For the speakers, giving at IHÉS: Alain Connes has written something these lectures are helpful to focus their thoughts. on this, as have Pierre Cartier and Maxim Having held a post at IHÉS, I am coming back Kontsevich. This idea of wanting to combine to IHÉS! I will be a holder of a Gelfand Chair, Grothendieckian ideas with quantum theory which represents a fantastic opportunity to in physics had been around for a long time. It come back to the Institute for three months I initially came to IHÉS to talk with Pierre was only later that I understood how to do it. every year over the next three years. IHÉS offers Cartier because I wanted to present a mathe- The key point is an operad structure on hyper- wonderful conditions. This year was the first matical result to him. “It’s a conjecture due to surfaces associated with Feynman diagrams. time that I stayed at the Ormaille residence, it’s Goncharov and Manin. It’s an open problem. You The latter were defined by Bloch, Esnault an aspect of life at the IHÉS that I hadn’t yet can’t write a one-page note without any proof”, and Kreimer using the Kirchhoff polynomial, experienced. There is a community spirit and was his comment. That was in 2005. I started discovered in the 19th century to study electrical comradeship which is not always obviously coming to IHÉS every week: I would fine-tune circuits. This operad structure is similar to a apparent to a permanent professor. But what I my proof, Pierre Cartier would challenge it and structure on moduli spaces of curves that I prefer the most is the Bois-Marie. When I am I would come back the following week. That used in my thesis. However, this coincidence stuck on a calculation I put my pen down and was how I ended up writing my thesis on the appeared to be superficial and at that time, take a walk in the woods to clear my mind. It moduli spaces of curves. we didn’t quite know what to do with it. To is wonderful to be in this intensely beautiful I owe the Institute my encounter with physics. unblock the situation required the concept natural environment and 20 minutes in the Dirk Kreimer was at IHÉS at the time; he of motivic periods – which came out of my woods can sometimes save hours of calculation. organised a conference on “Field theory, periods work on multizetas – and which, in certain and polylogarithms” in 2009 and invited me to situations, allows a rigorous construction of a Francis Brown present my results. Dirk was decisive in my Galois theory of periods. This applies perfectly developing a taste for physics, he has real talent in the physics situation and it’s by putting all for getting mathematicians interested in what these ideas together that Cartier’s dream can be he is doing. He had highlighted the structure made to come true: defining a “cosmic Galois of Hopf algebras on Feynman diagrams and had group” and drawing practical consequences for used it in his joint work with Alain Connes. particle physics from it. That is what I chose There were striking similarities with geometry. to present in my Cours de l’IHÉS this year. Together with Spencer Bloch, they had started to Both visiting and permanent professors come work on the question of motives in the context to listen to the lectures, which bring together of Feynman integrals. It was a very important all the people who are at the Institute at the

7 “séminaire de géométrie algébrique”

natural, would commute (or in the worst case scenario, anti-commute). It was therefore easy to take notes. And yet the content was incredibly innovative, rich and profound. It dealt with local duality in étale cohomology for torsion coefficients: Grothendieck formulated his famous conjectures at the beginning of the seminar on absolute purity and the existence of dualising complexes1. From there, Grothendieck would move on to the theory of cycle classes and to homology2 and then to the Lefschetz-Verdier formula, the Grothendieck-Ogg-Shafarevitch formula, his own Lefschetz formula on curves using the Nielsen-Wecken method and finally, during the second year (1965-66), to ℓ-adic sheaf theory and the rationality of L functions. Of course, he used the language of derived categories and functors from the start, which I discovered with delight. Fifty years on, arithmetic geometers still use this language daily. Although progress has Luc Illusie was a student of Alexander­Grothendieck not, alas, been there for SGA 1, 2, 3 or 4 and been made, conjectures have been demonstrated, and he attended the Séminaire de Géométrie would also have missed SGA 5 if Grothendieck new tools have appeared, the language itself, “the ­Algébrique (SGA). He spoke from Tokyo on hadn’t pressed me to come and listen to it six operations”, is essentially not a day older. 21 January during the IHÉS Paris-Beijing-­ and, making me very anxious, asked me to In the SGA 5 audience, I remember of course Tokyo Arithmetic Geometry Seminar. That write notes for his presentations. At the time, Grothendieck’s students: Berthelot 3, Demazure, day, the CNRS and IHÉS were inaugurating my understanding of algebraic geometry was Giraud, Jouanolou, Raynaud (Michèle et the ­“Laboratoire Alexander Grothendieck”. A rudimentary to say the least and I believed Michel), Verdier, and also the more “senior” perfect opportunity to remember the man that I would never be able to understand a ones: Dieudonné, Samuel, Serre (who came Luc Illusie calls the Master and to share his seminar of that level. To my surprise, however, occasionally), Tate (who spent the 65-66 memories of the SGA. I did. It was because of Grothendieck’s style. ­academic year in Paris). A young student of Tits Those who have had the privilege of listening called Pierre Deligne had arrived in January 65. I would first like to thank the organisers for the to him remember it. At the board, he was He attended the seminar but his presence was honour of being invited to say a few words to impressively dynamic but always methodical, barely noticed, such was his discretion. Soon, start the day, today being the inauguration of clear and rigorous. He would first carefully however, the Master spoke to me about him. the “Laboratoire Alexander Grothendieck”. go through the equipment that was required, Topos theory, étale cohomology presented basic The international reputation achieved by IHÉS explain the seminar’s goal and outline and then issues which neither he or Artin or Verdier could right from the start is clearly due to Grothendieck he would begin: a well-oiled mechanism would solve (existence of non-empty topos with no and in particular, to the seminars he conducted produce definitions, examples, statements points, coincidence of “base change” arrows during the sixties, the “SGAs”. They took place and (complete) demonstrations, following defined in two obvious possible ways). Child’s every week, on Tuesday afternoons. They were one another almost seamlessly. In discussing play for Deligne. There was nothing he could held in the former music room, converted to a corollaries and not tackle. library and then to a foyer which is now adjacent applications, he Of course, he used the language of The bulk of the to the Marilyn and James Simons auditorium. would not hesi- derived categories and functors from presentations They were long seminars, in the tradition of tate to launch were given by those given by Hadamard and Cartan. They into long the start, which I discovered with delight. Fifty Grothendieck, were spread over a year, sometimes two. They digressions, “ at least in the years on, arithmetic geometers still use this enabled an entire theory to be developped if he felt that first part of from its inception. They also played the usual these shed an language daily. SGA 5. In the social role of enabling mathematicians from interesting light second part, he different backgrounds, who shared here the on the topic. He liked to see mathematical had invited young ­colleagues to same interests and motivations, to meet and objects in all their facets. When I say “complete take over: Jouanolou, Bucur, Houzel. He liked interact. This type of seminar no longer exists. demonstrations” he did occasionally assert that to ask his students” to write his talks. They Its spirit can however still be found in certain such and such verification was “pure routine” learned their trade that way. His was a tough intensive work groups devoted to a single topic. and left it to the members of the audience. school. The Master was dauntingly demanding. I started attending the Grothendieck seminar That was the case especially for diagram I have told elsewhere4 of the long afternoons in the autumn of 1964. It was SGA 5. I had commutations: any diagram, if sufficiently I spent in his home examining one by one

8 “séminaire de géométrie algébrique”

the criticisms and suggestions with which he intersection theory. That year was, I think, a the keys to the seminar found themselves had covered the drafts I had submitted to him. sabbatical one for Grothendieck. In his eyes, being handed Deligne and Katz, rather like, in Results had to be presented in their natural Riemann-Roch was ancient history, and he 1960-61, Cartan had handed them to him for form which usually meant in the most general wasn’t sorry to let us, Berthelot and me, deal his seminar on analytic spaces. form. Everything had to be demonstrated. Any with the topic, in line with the notes he had It should also be mentioned that, from 1967 “It is clear that” or “It can easily be seen that” was given us, which we hastened to generalise as onwards, Grothendieck had been thinking banned. Mathematical content wad discussed much as possible. One day, he admitted to me about other matters. In a letter to Tate in May item by item and so was the order of the words that Berthelot was more “functorised” than he 1966, he had sketched a theory of crystals and in a sentence and punctuation. Length mattered was. Nevertheless, even if the Riemann-Roch of crystalline cohomology. He had developed it little. If a complement seemed interesting, it was theorem in itself no longer really interested him, in presentations given during the autumn of that welcome. We often didn’t finish before eight he was keen to develop intersection theory year, which were drafted by Coates and Jussila. in the evening. He would then invite me to a “in its natural context” i.e. on fairly general He then suggested to Berthelot that the latter simple dinner with his wife Mireille and their Noetherian patterns, using K-theory group write up the details for his thesis, “details” which children. After the meal, as we now know to a treat, he would tell me of be considerable. pieces of mathematics he During the same had been thinking about period, he worked lately. He would improvise on the interactions on a blank piece of paper, between this new using his fat pen, his writing theory, Serre and narrow and fast, sometimes Tate’s work on p- stopping on a symbol, to divisible groups and go over it again with his Dieudonné’s theory, pen lovingly. I can still hear issues which were his soft, melodious voice, to take up a good punctuated every now and chunk of his time then by a sudden “Ahft !” up right to the end when an objection came to of the sixties. At him. Then he would drive the same time, he me back to the station, where had given a series I would take the last train of talks on standard for Paris. conjectures (written Seminar sessions started at 2.30 pm and lasted filtration“without moving the cycles” (no moving by Kleiman) and on patterns. He was clearly an hour and a half. After the presentation, lemma). A method that was somewhat eclipsed not short of work. Nonetheless, he dreamt of participants were invited to take tea in the by Fulton’s work in the seventies but one that an SGA 8 seminar. He had thought of doing it salon in the administrative building. It was I believe to be more flexible and powerful in on abelian schemes. It is a real cause for regret a time for discussing a particular issue raised the end. For this topic, he had recruited other that it did not materialise, the literature on this during the seminar and exchanging ideas. speakers, who made important contributions topic now being scattered in many different Before the ­presentation, I would often go to it: Jussila, Kleiman, Raynaud. texts, sometimes not very satisfactorily. to the cafeteria. There I witnessed lively The autumn of 1967 saw the start of SGA 7, Despite all these beautiful problems which debates – of which I understood practically which, like SGA 5, was to last for two years. It occupied his thoughts - and I also have in nothing – between Grothendieck, Serre and was then that Grothendieck defined the nearby mind the “mysterious functor” problem he Tate. Actually, the ­discussions weren’t about cycle and the evanescent cycle functors (RΨ et set in 1970 and which was to be the starting the current seminar, they were about topics RΦ) 5, and used them in particular to establish point for Fontaine’s and many others’ work on for future seminars and ideas they had enlarged his semi-stable reduction theorem of abelian p-adic Hodge theory - from 1969 onwards, on in their ­correspondence: abelian variety varieties, together with his general theory of mathematics had ceased to be his sole focus. reduction, Tate curves, rigid geometry, patterns, biextension, a concept introduced by Mumford He had developed a new interest in physics etc. After lunch, the Master would sometimes shortly before. (he told me that he wanted to study Feynman’s take his pupils for a walk around the park, to In this study, he had needed for a technical lectures) and then turned to biology and finally, share his latest thinking. He had in that way point, a variant in étale cohomology of a specific to radical environmentalism, the consequences explained to Berthelot and me his reading of case of the classical Picard-Lefschetz formula of which are well-known. Manin’s article on formal groups, leading to his in topology. He admitted to not understanding When I think again of the sixties, those SGA conjectures on crystals and the specialisations a word of Lefschetz’s demonstration and had years, I see them as golden age of algebraic of their Newton polygons. therefore let Deligne explain it to him and geometry. A wind of freedom and innovation But I am ahead of myself. This conversation transcribe it in étale cohomology. He had also was blowing. Both the young and the not so was to take place in the year 1966-67, the year asked Katz to make the geometric preliminaries young laboured enthusiastically in the new of SGA 6, the seminar on Riemann-Roch and on Lefschetz’s pencils. That is how in 1968-69, fields that Grothendieck uncovered for us. The

9 Oppenheimer and IHÉS (1958-1967)

3. from January 1966. memory I want to keep of him is not that of 4. Reminiscences of Grothendieck and His School, Luc Illusie with the irascible hermit of later years. Rather, I Alexander Beilinson, Spencer Bloch, Vladimir Drinfeld et remember the brilliance of this exceptional al., Notices of the AMS, vol. 57, no.9, Oct. 2010, 1106-1115, mathematical who gave us fifty years ago, with and Grothendieck, magicien des foncteurs, INSMI, 22.12.2014, such generosity, so much. http ://www.cnrs.fr/insmi/spip.php ?article1097. Thank you. 5. However, the term “nearby cycles” only appeared in the seventies. Luc Illusie

Luc Illusie is a French mathematician, specialised in algebraic geometry. He was 1. In their most general form proposed by Grothendieck, a student of the mathematician Henri these conjectures were only solved much later, by Gabber, Cartan and from 1964, he also studied under the first one in 1994 and the second in 2005. Alexander Grothendieck. 2. he was the first to define this as cohomology with coefficients He was a research fellow, then a senior in the dualising complex – a brand new construction and ­research fellow at the mathematics generalisation of the “Borel-Moore homology”. ­laboratory of Université Paris-Sud, and became a professor there. From 1984 to 1995, he led the arithmetic and algebraic geometry team amongst others. He has been professor emeritus since 2005. In 2012, Luc Illusie was awarded the Émile Picard medal “for his fundamental work on the cotangent complex, the Picard-Lefschetz formula, Hodge theory and logarithmic geometry”..

10 Oppenheimer and IHÉS (1958-1967)

with Joseh Pérès. With Maurice Ponte (CSF), of scientific research in France and beyond Pierre Dreyfus and Fernand Picard (Régie in Europe and praised the excellence of the Renault), Motchane was looking for the mathematics section. As regards theoretical seed funding required to create his Institute. physics, however, he believed that Motchane These very supportive initial contacts enabled needed to bring proof of stable funding and him to quickly bring other industry leaders to move the Institute - located at that time on board (especially in the oil industry). It in two offices of the Fondation Thiers to was however not quite quickly enough for proper premises. This was needed to establish Oppenheimer - who was leaving on 17 May “the theorem of existence on which everything else - to attend the founding meeting as Motchane depends”, meaning the ability to attract physicists Robert Oppenheimer, Léon Motchane, 1963 had wished. The notice of invitation to the permanently. He declared himself ready to help General Meeting on 27 June 1958 formally the Institute in any way he reasonably could. Much has been written about Robert S. establishing the Institut des Hautes Études As things evolved and IHÉS having bought ­Oppenheimer (1904-1967), the famous Scientifiques association nevertheless bore Bois-Marie in Bures-sur-Yvette, in 1961 he ­American physicist and scientific director of his signature, as well as those of Joseph Pérès, seemed more confident and “hopeful for theoretical the Manhattan project; his charisma and career Dean of the Faculté des Sciences de Paris and physics in Europe and in the world”, with IHÉS have inspired a good dozen biographers. One Paul Montel, the President of Paris Académie finally recruiting its first theoretical physicist, aspect remains little known however: his role des Sciences de Paris. Louis Michel (1923-1999). in establishing the Institut des Hautes Études In Pérès’ office, Motchane, a man with a passion Scientifiques. for mathematics who obtained his doctorate at Oppenheimer’s visits IHÉS explicitly draws inspiration from the the age of 54 and who was responsible for the Visits by Oppenheimer were cleverly ­orchestrated model of the Institute for Advanced Study in bulk of the preliminary work, declared that he by Léon Motchane and reported in the press. Princeton (IAS). This research institute was wanted to “stem the French haemorrhage to the Oppenheimer’s presence was an event in itself founded in 1933, Oppenheimer becoming United States”. The Institute was born and he and his coming to lHÉS gave the Institute its director in 1947. IHÉS adopted its basic became its first director. important official recognition. Oppenheimer characteristics - the intellectual ones - as a He was delighted to announce the fact to was to come to IHÉS three times: from 16 to high level institute dedicated to basic research Oppenheimer by telegram. Notices soon 19 September 1959, on 17 and 18 October - and certain practical ones - such as the tra- appeared in the French and American press in 1961 (in Bures, although the Institute had not dition of tea being served daily, conducive to the summer of 1958. In the autumn, Motchane moved there yet), and from 14 to 17 May 1963. exchanges of views. Of equal importance was visited IAS to see Oppenheimer and also His last visit, planned for 1965, was cancelled the relationship between Oppenheimer and Chicago, to settle the details of mathematicians for health reasons. Léon Motchane (1900-1990), the founder and Jean Dieudonné and Alexander Grothendieck’s The programme of a visit was planned very first director of IHÉS. As life member of the recruitment. He had probably approached carefully to allow for official scientific discussions scientific committee, advisor to the director, them beforehand, in any case no later than (meeting of the scientific committee) and for frequent visitor and regular correspondent, the International Congress of Mathematicians private ones with company directors (French Oppenheimer played a major role in the crucial which took place in Edinburgh. industry leaders, members of EURATOM) as early years at IHÉS. It was the start of a long relationship between well as meeting with the key players in higher Oppenheimer and Motchane, who exchanged education and research in France. For example, in Beginnings and inspiration long letters and short telegrams on all aspects 1959, he had lunch with Gaston Berger, director The first meeting between Oppenheimer of life at IHÉS. During his annual visit to of higher education and Pierre Massé, Planning and Motchane probably goes back to 1948. Oppenheimer in 1962, this is how Motchane Commissionier. He dined with Pierre Piganiol It is mentioned by Freeman Dyson and described its importance: “There is no doubt who was the general delegate for scientific commented on by Cécile DeWitt-Morette, that I come mainly to see you and to have two or research. He also had time to visit the future who was at the time at IAS. Oppenheimer three good conversations with you, as we do every Bois-Marie site and to talk with physicists. was its new director and Motchane a ­business year. By discussing the problems we both encounter, Each of these meetings was an opportunity man, often staying during his frequent speaking in friendship of things and of men - because for Oppenheimer to speak favourably of IHÉS business trips with his brother Alexandre the Institute is a human affair - by listening to you, and to place it in the broader scope of scientific Motchane, who lived in Monclair in New I am able to outline a way forward which seems to research development. Jersey. It was probably through Alexandre, a take us in the right direction.” The Directors of the Board were enthusiastic chemical engineer, that he was able to meet about their meetings with Oppenheimer. In Oppenheimer. Hopeful for theoretical physics fact, some of them visited him in Princeton, But the true beginning for IHÉS and Was Oppenheimer truly convinced by their status as IHÉS Board member serving Oppenheimer’s contribution started in 1958. Motchane’s project, in which he had agreed as introduction, when they travelled to the In the spring of 1958 Oppenheimer was in fact to take part? Whilst defending it in public, he United States (as René Grandgeorge, Managing in Paris. He was giving a series of conferences expressed a few concerns in private in 1959. He Director of Saint Gobain, did in 1960, Fernand at the Sorbonne which aroused much interest. said that he was hopeful for the possibilities that Picard of Régie Renault in 1961, Léon Kaplan Motchane met him and organised a meeting such an institute could offer to the development of Société Shell France in 1962).

11 Setting up the theoretical physics section Louis Michel and Harry Lehmann, then both The American Committee for the Institute for Oppenheimer was a life member of the IHÉS permanent professors of theoretical physics, Advanced Study – Europe, Inc. (1964 -1971) scientific committee. He was also a theoretical put forward the name of David Ruelle, who In the summer of 1958, when the creation of physicist and, as IAS director, came into contact was recommended by Jost and Wightman. IHÉS was being announced in the American with many other theoretical physicists staying press, Oppenheimer received a letter from there. He played a key role in setting up the Brakeley, a fundraising agency, asking whether theoretical physics section at IHÉS. Whereas the it would be opportune to develop a support mathematics section established itself quickly group for the Institute. It was only a few years around Dieudonné and Grothendieck, it was not later, in 1963, that the IHÉS Chairman, André the case for theoretical physics, even though it Grandpierre - the Chairman of Pont-à-Mousson, quickly welcomed very brilliant and enthusiastic he took over from Joseph Pérès on the latter’s physicists – but none permanently. Gell-Mann, death in 1961 - put this idea to the Board for instance, hesitated for a long time over members. This followed the suggestion from whether to accept but refused in the end, an American academic, Irving Michelson, in despite discussions with Oppenheimer and the Nancy for the year. By then, IHÉS had in fact fact that the terms he had asked for had been started to become very well known in the United met by Motchane. States and the proportion of American visits Oppenheimer’s input was decisive in at least had always been very important (around 30%). three instances including the recruitment of Before taking a decision, Motchane asked two permanent professors. Oppenheimer for his view on the idea, as well as Relations between IHÉS and academics had information on the Sam Swerdloff agency they not always been smooth and Oppenheimer was had selected to launch a fundraising campaign: sometimes taken to task. From 1959, Motchane “in Europe, we are not used to this way of doing had sought Michel’s advice on invitations to things” he writes. Having received a telegram physicists and in 1961 offered him, with the from Oppenheimer and favourable reports of support of the scientific committee, the post Swerdloff, Grandpierre convened a meeting of of permanent professor. Maurice Lévy, then the Board members on 18 September 1963 at holder of the Chair of theoretical and high the Fondation Thiers, when they decided to energy physics considered this initiative to be New York Times, Sunday, September 24, 1959 set up this support committee. “shocking and immoral” as the offer competed Swerdloff, having met Oppenheimer, would with academia, depriving the university of a start by coordinating the production of a good professor and a “research-leader” it lacked. However, Ruelle was being sounded out for brochure, with statements from French He shared his concerns with Oppenheimer, a post at IAS. Motchane wanted “to avoid at industry leaders as well as from American asking him to use his influence with Motchane any cost anything resembling competition between scientists like Wightman, explaining what to change the latter’s mind. He ended his the two Institutes” and shared his views with IHÉS meant to them. Oppenheimer himself letter by promising “a bitter battle should that Oppenheimer, who told him on no account validated the name used for the campaign: not be the case”. In response, Oppenheimer to limit his freedom of action and that this Institute for Advanced Study-Europe, which chose to favour developing IHÉS. He justified did not preclude IAS from making an offer is the English translation of Institut des Michel’s recruitment to Lévy, pointing out itself. This high level of trust between the two Hautes Études Scientifiques, but beyond that, the entire scientific committee’s endorsement directors endured. Ruelle accepted the post recognition of what IHÉS had become: the and adding that the decision would on the at IHÉS in September 1963. European counterpart to the IAS in Princeton. contrary benefit academia, physics and its Finally, Oppenheimer had a very clear vision Motchane thanked him: “I am very touched by consolidation in the Paris region. Nonetheless, of developing theoretical physics and of the this analogy, which is a promotion”. Lévy persisted in believing that Motchane’s way it should be implemented at IHÉS, which Motchane went to the United States in offer was fundamentally a bad thing and added Motchane shared: “physics should not be forgotten December 1963 and in a few days, enlisted that Cartan and Schwarz shared his opinion; in theoretical physics”. When the possibility the support of American industry leaders (such they leant on Michel to refuse, arguing it of replacing Harry Lehmann in 1965 arose, as International Nickel, United States Steel, would create a precedent. Oppenheimer Oppenheimer was in favour of recruiting John Manville, Union Carbide, IBM), to whom having passed on Lévy’s letter to him, Michel a physicist “concerned with the actualities of he was introduced by IHÉS Board members. would explain to Lévy in a thoughtful letter present experimental explorations of fundamental He was delighted to report to Oppenheimer: that he saw this post he had just accepted at physical problems”. He recommended Léon “I find it quite extraordinary that our vague project IHÉS as another way of organising theoretical Van Hove - who hesitated for a long time of an American support group should have come into physics in France and of paving the way before refusing because of the administrative being so quickly in such excellent conditions – let all for future cooperation between IHÉS and work he foresaw - rather than Vladimir Glaser, our friends be praised and thanked!” universities. for whom he had great esteem, but who did The founding luncheon of the American Oppenheimer intervened again at the time not fit into the desired development of the Committee for the Institute for Advanced Study of David Ruelle’s recruitment. In June 1963, theoretical physics section. – Europe, Inc., which took place on 11 March

12 1964, was an opportunity for Oppenheimer, who in the discussions concerning the creation of had agreed to make up its scientific committee the European University that European States together with Richard Courant, to express wanted to see. This project resulted in curbing his views about IHÉS. This is how Motchane European contributions to IHÉS, which would reported what he said: “Finally, Oppie spoke like no longer be deemed necessary. Oppenheimer’s a philosopher, saying that he had always wanted to opinion was frequently sought and in discussion see a competitor emerging, how three-quarters of those or letters, he never ceased to make the case who come to us have already been to Princeton, that for IHÉS’ existence and the need to fund it. this was not the result of any agreement between Mr In this way was his input largely instrumental Motchane and himself but was in the nature of things. in EURATOM supporting IHÉS from 1960. He said that our Institute had achieved infinitely more in the first five years of its existence than Princeton Let Léon Motchane conclude with these last words in the corresponding period. He explained why better to Kitty Oppenheimer, soon after her husband’s work is done in this type of institute.” passing: “The image of your husband lives on in The decision of the Inland Revenue Service in everyone’s memory, rich and varied, with everyone the United States on 29 December 1964 allowed finding something of their own aspirations. tax deductions which had initially been seen as During our meetings on Institute business for difficult to obtain. Subscriptions, some already the past nine years, I was able to appreciate his acquired from the start, followed. For six years, profound humanity, his discernment of young people’s the American committee contributed up to character, his idealism that made him take on a cause 10% of the budget, contributions decreasing Robert and Kitty Oppenheimer at IHÉS, 1963 wholeheartedly if he felt it to be a worthy one. When gradually. in the autumn of 1970 and the last cheque our Institute was founded, he agreed enthusiastically The main players of the American committee received on 8 February 1971. to be part of it and lent the entire support of his were Henry S. Wingate (International Nickel In no way did this mark any downturn in authority to our young theoretical physics section Cy of Canada), together with Albert P. Gagnebin IHÉS’ relations with the United States, quite which sorely needed it. We have lost a faithful and (International Nickel Co., New-York), then the opposite. The following years saw as many attentive friend.” Harold W. Fisher (Standard Oil Company) and American visitors as ever and discussions began Emanuel Piore (IBM corp.). The two presidents, with the National Science Foundation, as well Anne-Sandrine Paumier Wingate and Fisher, took part in the IHÉS as with the National Academy of Science. And Board (1964, 1969). surely the creation of Friends of IHES, Inc. The existence, the successes of the American in 1999 can be seen as a rebirth of this first committee and its warm welcome enabled American committee! Motchane and Grandpierre to approach American foundations, as they did by contacting­ Oppenheimer and European science Warren Weaver, of the Sloan Foundation, On a broader level, in Oppenheimer’s mind (as for instance, following a suggestion and an we have seen in the description of his hopes introduction from Oppenheimer. for theoretical physics in Europe), IHÉS truly In 1967, the support committee considered a had to play the part of a European institute. campaign to reach the level of funding asked His commitment to IHÉS was part of his wider for by Motchane, or 30% of IHÉS’ income, activities in the interest of the “European scientific Mathematical historian, matching the percentage of American visitors renewal”. His speech during the inauguration Anne-Sandrine Paumier is currently a in the year 1966-67. To that end, the American of the Synchrotron Proton at CERN in 1960, ­postdoc at IHÉS, where she works on the committee recommended that Motchane launch reported by Motchane, bears witness to this ­history of the Institute, drawing on its a similar campaign in Europe, to increase long-standing attachment to European science: archives and the memories of the people non-French European funding and to boost “I am among those who owe almost everything of connected with it. American investors’ confidence. Unfortunately, their formal education to Europe, as do many of my A mathematician by training (École Normale the committee struggled. Faced with his failure generation in our country. We are glad that we can be Supérieure de Lyon), she obtained her PhD to find new members, Harold Fisher decided confident that our children, and our children’s children, from the Institut de Mathématiques de to call an end to the venture. The reasons will be coming back to Europe for a renewal of the great Jussieu with a thesis on “Laurent Schwartz he put forward to explain the difficulty in tradition which binds us together.” But his work was (1915-2002) and the collective mathematical renewing membership were the recession, the in no way limited to perpetuating an existing life”. Her field of research is “mathematical fact that this was an institute for advanced study, European scientific tradition. Paying tribute geography” after the second world war, that therefore far removed from industry and most to Oppenheimer, Jules Guéron, chemist and is, the various “places” for mathematics importantly, the impression that it was up to EURATOM scientific director, wanted to follow specific to the period and their impact on Europe to fund IHÉS, as American industry “the modern European side of Oppenheimer”, who mathematicians’ work and on the mathema- leaders were preferring American institutions. was interested in all European scientific projects. tics produced. The dissolution of the committee was decided Indeed, Oppenheimer, like Motchane, took part

13 international campaign friends of IHES gala dinner in New York

The third Friends of IHES Gala was held on The fundraising objective was more than doubled 18 November at the Intrepid Sea, Air & Space with $662 308 collected that evening thanks Museum in New York. especially to the Simons Foundation matching system, enabling research visits in Bures of The evening was chaired by Marwan Lahoud scientists from all over the world to be funded. and its theme was Math & Physics Exploring The Institute thanks its American friends for Space. The dinner was a dynamic mingling of their support and generosity. legends in science, space and business, who share The next Friends of IHES gala dinner will take a passion for exploring the universe. place on 4 November 2015 at the Pierre Hotel Professor Thibault Damour was the speaker in New York and the theme will be Math and of honour and provided historical insights Games of Chance. into the concept of Space. Doctor Charles Simonyi shared his extraordinary experience Charles Simonyi of spaceflight missions.

conference Friends of IHES held a mathematical finance conference, An Analysis of 180 Years of Market Drawdowns on 30 June 2015 in the New York offices of AXA, a major IHÉS Fiftieth Anniversary Campaign donor. The presentation was made by Dr Robert J. Frey, Director, Program in Quantitative Finance, Stony Brook ­University Friends of IHES’ Directors of the Board and former hedge fund managing ­director. Around fifty scientists and financiers ­participated in this fascinating conference which generated many questions. setting up a Support Committee

Watch the video of the event The IHÉS Support Committee met on during the directly: 7 July 2015 to set the international fundraising two previous strategy for IHÉS and the conditions for campaigns launching the third fundraising campaign. are clear This new strategic phase will enable clear indications of Philippe Camus André Lévy-Lang goals to be defined and to meet the Institute’s the merits of IHÉS’ efforts. ambitions for the coming years. A Campaign Committee is being set up, to A private institution, IHÉS has benefitted since monitor the projects undertaken in the various its creation from the generosity of sponsoring strands of IHÉS’ development strategy. IHÉS is companies and philanthropists. The arrival of new proud to announce that Philippe Camus and partners and the renewal of historical support­ André Lévy-Lang have agreed to co-chair it.

14 conference cycle with Société Générale Private Banking

Since the autumn of 2013, Société Générale Pierre Vanhove, CEA senior researcher at IHÉS, a wider audience and they show the public’s Private Banking has been co-organising with also contributed to the series by giving a interest in highly theoretical topics. IHÉS a series of scientific conferences in France conference on gravitation in Luxemburg. This and in the rest of Europe. proved to be a scientific epic, covering Aristotle, Newton and the Copernican revolution. The Thibault Damour, Permanent Professor at IHÉS link was made between the nature of gravity and since 1989 held a conference in Monaco and our vision of the cosmos, leading us to rethink in Geneva. In his talk, “Troublants trous noirs” he gravitation and answer fundamental questions described this phenomenon, a most fascinating on the nature of the Universe. prediction of Einstein’s theory of General IHÉS is delighted to partner with one of its Relativity. He also showed their crucial role not major Fiftieth Anniversary Campaign donors. only in Astrophysics but also in Particle Physics. These lectures are real opportunities to reach Pierre Vanhove a one-million-euro gift from Huawei

At the end of 2014, Huawei, a leading global to the most fundamental of sciences.” commented provider of information and communications Emmanuel Ullmo. technology solutions, announced a one-million- The “Huawei fund”, created in 2010 with euro gift to IHÉS. 250 000 euros, will now enable support to be provided in perpetuity for the visits of IHÉS in UK This gift comes as part of the R&D plan carried mathematicians. “We are proud to bring our support out by Huawei in Europe and in France in to IHÉS whose dynamism and expertise produce On 9 June 2015, Emmanuel Ullmo was particular, in the field of mathematics. Huawei many initiatives designed to support fundamental invited by Sylvie Bermann, French Ambassador wishes to support excellence in research locally, research.” said Mr Karl Song, Managing Director in the United Kingdom to present the giving it international visibility downstream. of Huawei France. Institute’s development activities. A dozen For this reason, Huawei decided to renew For its part, IHÉS is delighted with this new participants attended the lunch, organised its support to IHÉS. “The Huawei research partnership and wishes to convey its deepest to raise awareness of IHÉS and build new programme in France is a particularly ambitious one, thanks to Huawei. partnerships. and this new gift illustrates Huawei’s commitment After two conferences already organised in 2013 and 2014 by Rémi Bourrette and Rama Cont, members of the IHÉS Support Committee, this invitation marks a decisive step forward for the development strategy in the UK. IHÉS would like to thank Ambassador Bermann and Cyrille Van Effenterre, Science and Technology Counsellor, for their support.

Mérouane Debbah, Emmanuel Ullmo

15 point of view of...

Shigenori Seki is a Japanese researcher in called “Philosopher’s Walk”. In the 20th century, theoretical physics. He obtained his PhD in Kitaro Nishida, professor of philosophy at Kyoto 2002 in Kyoto University (Japan). Since then, he University, walked on this path for meditation. An has been travelling extensively in Japan, Israel, appropriate place to go for a walk is important South Korea and regularly in France, at IHÉS. for the research of fundamental science and philosophy! From one o’clock we have lunch Since Saclay is on the plateau, it is good exercise My first visit at IHÉS was in November 2009. together at the IHÉS cafeteria. The lunch is for me to climb to IPhT. My collaborator, Prof. I moved from Tel Aviv and had a wonderful table service and takes about one hour. From Robi Peschanski, is at IPhT. Our collaboration time at IHÉS for two years as a postdoc. The four o’clock we gather in the salon for a tea was initiated in 2009 during my first stay at residence in Ormaille is well equipped and break. So lunch and tea are suitable times to chat IHÉS. At that time, we were interested in the the IHÉS staff supported me to install myself with researchers in various subjects. I have been scattering of particles in the context of the (e.g. to obtain a carte de séjour). Therefore I studying string theory, which is at the interface AdS/CFT correspondence, and succeeded in could start my research without any trouble. between physics and mathematics. Even if I publishing a paper. My collaboration with Robi Fortunately, I have visited IHÉS again for one do not completely understand my colleagues’ is still continuing. Recently one of my research or two months every year since 2011. IHÉS researches, they stimulate my consideration and topics has been quantum entanglement. During provides us with complete freedom, so that attract my interest. I think unexpected creativity my last stay, we had fruitful discussions about I have had many opportunities for scientific is sometimes born of such communications the entanglement of interacting particles in a activities (e.g. seminars, workshops, collaboration, with different research worlds. scattering process. etc.) in France. Paris is one of the most active centres of research The atmosphere in IHÉS always refreshes My day at IHÉS begins with a calm morning. in string theory. There are many institutes my brain. What atmosphere is it? Calm and I buy a pain au chocolat at the bakery on my and universities in the region of the Grand stimulating. Life at IHÉS is calm, and I can way to the Institute, and then concentrate on Paris. IHÉS is in Bures-sur-Yvette, which is meditate on problems deeply in the quiet research. IHÉS is located in Le Bois-Marie, a quiet village and is not far from Paris. So I environment. At the same time, IHÉS provides which is a quiet forest. I sometimes walk there can easily access seminars and conferences, and interactions between the researchers coming for relaxation and meditation. This environment, contact researchers in the Paris region. Actually from all over the world, so that the unentangled which is different from the office, helps me to I attended the series of seminars, “Rencontres researchers become entangled. Such interactions organise my thoughts. Near Kyoto University théoretiennes”, at Institut Henri Poincaré twice a stimulate my mind. in Japan, which I graduated from, there is a month. I also often visited IPhT/CEA-Saclay. It pedestrian path along a narrow canal which is takes thirty minutes on foot from IHÉS to Saclay. : I. Peeters, H. Wilkinson : I. Peeters, Landais - Translation agenda 2015/2016 -

22 September to 6 October 2015, every ­Tuesday, 23 - 27 November 2015 23 - 27 May 2016 IHÉS Topos à l’IHÉS, organised by O. Caramello, P. Cartier, Colloquium as part of the Trimester Program on Cours de l’IHÉS: L. Lafforgue, Catégories ­syntactiques A. Connes, S. Dugowson et A. Khelif. Nonlinear Waves. pour les motifs de Nori. November 2015 20 - 24 June 2016 aillat, V. Touchant V. aillat, 23 to 25 September 2015 Conference by T. Damour organised by Les Amis de l’IHÉS Colloquium as part of the Trimester Program on C Algebraic Geometry - A conference in honour of 14 - 18 December 2015 Nonlinear Waves. Arthur Ogus on the occasion of his 70th birthday, Cellular and Molecular Biotechnology, entretiens 18 - 29 July 2016 organised by A. Abbes and L. Illusie. interdisciplinaires de Bures organised by F. Képès, Summer School as part of the Trimester Program on 13 to 15 October 2015, Université Paris-Sud/ M. Gromov et N. Morozova. Nonlinear Waves. IHÉS January to February 2016 Journées Mathrice d’automne 2015, meeting for Cours de l’IHÉS: T. Damour, Ondes gravitationnelles mathematics laboratories’ Systems and Network et systèmes binaires. Administrators January to February 2016 October 2015 Cours de l’IHÉS: H. Duminil-Copin, Le modèle d’Ising Cours de l’IHÉS: J. Pardon, Contact Homology and en dimension d. Virtual Fundamental Cycles. March - April 2016 12 October 2015 Cours de l’IHÉS: E. Ullmo, La conjecture d’André-Oort. Start of the Université Paris-Saclay Doctoral May - June 2016 Schools of Mathematics. Cours de l’IHÉS: E. Rabinovici, Topics in Quantum October - November 2015 Field Theory and String Theory. Cours de l’IHÉS: C. Villani, La théorie synthétique de 2 May - 29 July 2016

la courbure de Ricci. Trimester Program (seminars, workshop and collo- M. C. Brisson, layout: and - Text M.-C. Vergne Dars, J.-F. 4 November 2015, Pierre Hotel, New York quium) on Nonlinear Waves, organised by Y. Martel, F. Merle, F. Planchon, P. Raphaël and J. Szeftel.

Gala dinner organised by Friends of IHES. Photos: